Class::Data::Inheritable(3pm)

1Class::Data::InheritablUes(e3r)Contributed Perl DocumentCaltaisosn::Data::Inheritable(3)
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NAME

6       Class::Data::Inheritable - Inheritable, overridable class data
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SYNOPSIS

9         package Stuff;
10         use base qw(Class::Data::Inheritable);
11
12         # Set up DataFile as inheritable class data.
13         Stuff->mk_classdata('DataFile');
14
15         # Declare the location of the data file for this class.
16         Stuff->DataFile('/etc/stuff/data');
17
18         # Or, all in one shot:
19         Stuff->mk_classdata(DataFile => '/etc/stuff/data');
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DESCRIPTION

22       Class::Data::Inheritable is for creating accessor/mutators to class
23       data.  That is, if you want to store something about your class as a
24       whole (instead of about a single object).  This data is then inherited
25       by your subclasses and can be overridden.
26
27       For example:
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29         Pere::Ubu->mk_classdata('Suitcase');
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31       will generate the method Suitcase() in the class Pere::Ubu.
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33       This new method can be used to get and set a piece of class data.
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35         Pere::Ubu->Suitcase('Red');
36         $suitcase = Pere::Ubu->Suitcase;
37
38       The interesting part happens when a class inherits from Pere::Ubu:
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40         package Raygun;
41         use base qw(Pere::Ubu);
42
43         # Raygun's suitcase is Red.
44         $suitcase = Raygun->Suitcase;
45
46       Raygun inherits its Suitcase class data from Pere::Ubu.
47
48       Inheritance of class data works analogous to method inheritance.  As
49       long as Raygun does not "override" its inherited class data (by using
50       Suitcase() to set a new value) it will continue to use whatever is set
51       in Pere::Ubu and inherit further changes:
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53         # Both Raygun's and Pere::Ubu's suitcases are now Blue
54         Pere::Ubu->Suitcase('Blue');
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56       However, should Raygun decide to set its own Suitcase() it has now
57       "overridden" Pere::Ubu and is on its own, just like if it had
58       overridden a method:
59
60         # Raygun has an orange suitcase, Pere::Ubu's is still Blue.
61         Raygun->Suitcase('Orange');
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63       Now that Raygun has overridden Pere::Ubu further changes by Pere::Ubu
64       no longer effect Raygun.
65
66         # Raygun still has an orange suitcase, but Pere::Ubu is using Samsonite.
67         Pere::Ubu->Suitcase('Samsonite');
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Methods

70   mk_classdata
71         Class->mk_classdata($data_accessor_name);
72         Class->mk_classdata($data_accessor_name => $value);
73
74       This is a class method used to declare new class data accessors.  A new
75       accessor will be created in the Class using the name from
76       $data_accessor_name, and optionally initially setting it to the given
77       value.
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79       To facilitate overriding, mk_classdata creates an alias to the
80       accessor, _field_accessor().  So Suitcase() would have an alias
81       _Suitcase_accessor() that does the exact same thing as Suitcase().
82       This is useful if you want to alter the behavior of a single accessor
83       yet still get the benefits of inheritable class data.  For example.
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85         sub Suitcase {
86             my($self) = shift;
87             warn "Fashion tragedy" if @_ and $_[0] eq 'Plaid';
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89             $self->_Suitcase_accessor(@_);
90         }
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AUTHOR

93       Original code by Damian Conway.
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95       Maintained by Michael G Schwern until September 2005.
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97       Now maintained by Tony Bowden.
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BUGS and QUERIES

100       Please direct all correspondence regarding this module to:
101         bug-Class-Data-Inheritable@rt.cpan.org
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COPYRIGHT and LICENSE

104       Copyright (c) 2000-2005, Damian Conway and Michael G Schwern.  All
105       Rights Reserved.
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107       This module is free software. It may be used, redistributed and/or
108       modified under the same terms as Perl itself.
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